Exhaust apparatus for transverse engine

ABSTRACT

Disclosed is an exhaust apparatus (E) for a transverse engine ( 1 ) coupled with a transmission ( 11 ) located on one side thereof in a cylinder arrangement direction. The exhaust apparatus (E) has an upstream exhaust assembly ( 48 ) which comprises a plurality of branch pipe portions ( 32 ), a single exhaust pipe portion ( 34 ), and an exhaust gas-purifying unit ( 40 ). The exhaust gas-purifying unit ( 40 ) is disposed on a vehicle-rear side of the engine ( 1 ) to allow a gas passage thereinside to extend approximately in a vehicle-widthwise direction, in top plan view. The upstream exhaust assembly ( 48 ) includes, on an exhaust upstream side of the single exhaust pipe portion ( 34 ), a section which curves to allow an exhaust downstream region of the section to be oriented toward one side of the vehicle-widthwise direction which is a direction coming close to the transmission ( 11 ), in top plan view. The single exhaust pipe portion ( 34 ) curves to allow an exhaust downstream region of the single exhaust pipe portion ( 34 ) to be oriented toward a vehicle-front side, in top plan view. This makes it possible to compactly lay out the upstream exhaust assembly ( 48 ) in an engine compartment ( 19 ) without sacrificing a passenger compartment space, and quickly raise a temperature of a catalyst in the exhaust gas-purifying unit ( 40 ) during warm-up of the engine ( 1 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention belongs to a technical field relating to anexhaust apparatus for a transverse engine which is transversely placedin an engine compartment at a front of a vehicle to allow a cylinderarrangement direction to be oriented in a widthwise direction of thevehicle (vehicle-widthwise direction).

2. Description of the Background Art

Heretofore, this type of transverse engine has been widely known.Typically, an exhaust apparatus for the transverse engine is disposed ona vehicle-rear side of the engine (see, for example, JP 2008-260472A;this document will hereinafter be referred to as “Patent Document 1”).The exhaust apparatus has a plurality of branch pipe portions eachcommunicated with a respective one of a plurality of cylinders of theengine, wherein the branch pipe portions are merged to finally form asingle exhaust pipe portion. Specifically, in the Patent Document 1, theentire cylinders (four cylinders) are divided into a plurality ofcylinder groups each consisting of two or more cylinders whose exhauststrokes are not successive with respect to each other (a cylinder groupconsisting of the first (#1) and fourth (#4) cylinders, and a cylindergroup consisting of the second (#2) and third (#3) cylinders), and thebranch pipe portions communicated with respective ones of the cylindersin each of the cylinder groups are merged on a cylindergroup-by-cylinder group basis to form a plurality of (two) intermediatecollector pipe portions. Then, the two intermediate collector pipeportions are merged together to form a single exhaust pipe portion. Insome cases, all of the branch pipe portions are merged together to forma single collector pipe portion, without providing the intermediatecollector pipe portions.

In late years, with a view to reducing exhaust gas emissions duringengine warm-up (when an engine is in a cold start mode), an exhaustgas-purifying unit has been provided on a relatively upstream side of anexhaust gas stream to quickly raise a temperature of a catalyst in theexhaust gas-purifying unit. In the Patent Document 1, an exhaustgas-purifying unit (manifold catalytic converter) is provided in each ofthe intermediate collector pipe portions.

Meanwhile, in view of enhancing engine exhaust efficiency to increaseengine output power, it is desirable to maximize a length of each of thebranch pipe portions and the intermediate collector pipe portions (in anexhaust apparatus provided with no intermediate collector pipe portion,to maximize a length of each of the branch pipe portions). From thisviewpoint, the exhaust apparatus in the Patent Document 1 is alsodesigned to increase a length of each of the branch pipe portions andthe intermediate collector pipe portions. For this purpose, the twointermediate collector pipe portions are disposed inside a tunnelportion formed in a vehicle-widthwise central region of a floor panel.

However, in order to allow the two intermediate collector pipe portionsto be disposed inside the tunnel portion, it is necessary to increasewidth and height dimensions (cross-sectional area) of the tunnelportion. Particularly, in the Patent Document 1, due to the exhaustgas-purifying units provided in the intermediate collector pipeportions, the cross-sectional area of the tunnel portion needs to befurther increased. Thus, there remains the need for improvement in viewof ensuring a passenger compartment space as widely as possible.Moreover, in the arrangement where the exhaust gas-purifying unit isprovided inside the tunnel portion, a traveling wind produced bytraveling of a vehicle is more likely to touch the exhaust gas-purifyingunit, so that it becomes difficult to quickly raise a temperature of acatalyst in the exhaust gas-purifying unit during engine warm-up. Inthis regard, there also remains the need for improvement.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above background art.It is therefore an object of the present invention to, in an exhaustapparatus for a transverse engine, make it possible to compactly lay outan upstream exhaust assembly thereof including an exhaust gas-purifyingunit, in an engine compartment without sacrificing a passengercompartment space, and quickly raise a temperature of a catalyst in theexhaust gas-purifying unit during engine warm-up.

In order to achieve the above object, the present invention is directedto an exhaust apparatus provided in an engine having a plurality ofcylinders arranged in a line, wherein the engine is transversely placedin an engine compartment at a front of a vehicle to allow a cylinderarrangement direction to be oriented in a vehicle-widthwise direction,and coupled with a transmission located on one side thereof in thecylinder arrangement direction. The exhaust apparatus comprises anupstream exhaust assembly connected to a surface of the engine on avehicle-rear side, and a downstream exhaust pipe provided on an exhaustdownstream side of the upstream exhaust assembly. The upstream exhaustassembly includes: a plurality of branch pipe portions communicated withrespective ones of the plurality of cylinders and extending from thevehicle-rear-side surface of the engine toward the vehicle-rear side; asingle exhaust pipe portion provided on the exhaust downstream side ofthe plurality of branch pipe portions in such a manner that it iscommunicated with the branch pipe portions; and an exhaust gas-purifyingunit connected to an exhaust downstream end of the single exhaust pipeportion. The exhaust gas-purifying unit is disposed on the vehicle-rearside of the engine to allow a gas passage thereinside to extendapproximately in the vehicle-widthwise direction, in top plan view. Theupstream exhaust assembly includes, on an exhaust upstream side of thesingle exhaust pipe portion, a section which curves to allow an exhaustdownstream region of the section to be oriented toward one side of thevehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view. The single exhaust pipe portion curvesto allow an exhaust downstream region of the single exhaust pipe portionto be oriented toward a vehicle-front side, in top plan view. Thedownstream exhaust pipe is connected to an exhaust downstream end of theexhaust gas-purifying unit, and disposed to extend from a connectionportion thereof with the exhaust gas-purifying unit toward an tunnelopening formed in a vehicle-widthwise central region of a lower end of adash panel of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing a mounted state of an exhaustapparatus according to a first embodiment of the present invention, withrespect to a vehicle.

FIG. 2 is a side view showing the mounted state of the exhaust apparatuswith respect to the vehicle, when viewed from a left side of thevehicle.

FIG. 3 is a top plan view showing an upstream exhaust assembly, and anupstreammost one of a plurality of divided pipe members of a downstreamexhaust pipe, in the exhaust apparatus.

FIG. 4 is a side view showing the upstream exhaust assembly, and theupstreammost pipe member of the downstream exhaust pipe, in the exhaustapparatus, when viewed from the left side of the vehicle.

FIG. 5 is a view showing the upstream exhaust assembly, and theupstreammost pipe member of the downstream exhaust pipe, in the exhaustapparatus, when viewed from a rear side of the vehicle.

FIG. 6 is a view corresponding to FIG. 3, illustrating a secondembodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 4, illustrating the secondembodiment.

FIG. 8 is a view corresponding to FIG. 5, illustrating the secondembodiment.

FIG. 9 is a view corresponding to FIG. 3, illustrating a thirdembodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 4, illustrating the thirdembodiment.

FIG. 11 is a view corresponding to FIG. 5, illustrating the thirdembodiment.

FIG. 12 is a view corresponding to FIG. 3, illustrating a fourthembodiment of the present invention.

FIG. 13 is a view corresponding to FIG. 4, illustrating the fourthembodiment.

FIG. 14 is a view corresponding to FIG. 5, illustrating the fourthembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be specifically described based onembodiments thereof.

First Embodiment

FIGS. 1 and 2 show an exhaust apparatus E according to a firstembodiment of the present invention. The exhaust apparatus E is designedfor a transverse engine 1. The engine 1 is an inline four-cylinderengine having four cylinders 2 arranged in a line, and transverselyplaced in an engine compartment 19 at a front of a vehicle to allow acylinder arrangement direction to be oriented in a vehicle-widthwisedirection (rightward-leftward direction in FIG. 1). In the followingdescription, a right side of the vehicle which corresponds to a rightside in FIG. 1 (reverse side of the drawing sheet of FIG. 2), a leftside of the vehicle which corresponds to a left side in FIG. 1 (obverseside of the drawing sheet of FIG. 2), a front side of the vehicle whichcorresponds to an upper side in FIG. 1 (left side in FIG. 2), and a rearside of the vehicle which corresponds to a lower side in FIG. 1 (rightside in FIG. 2), will be referred to respectively as “vehicle-rightside”, “vehicle-left side”, “vehicle-front side”, and “vehicle-rearside”.

The engine 1 is disposed offset toward a vehicle-right side (right sidein FIG. 1) in the engine compartment 19. Further, the engine 1 isdisposed in an inclined posture to allow an axis of each of thecylinders 2 to be oriented upwardly and toward a vehicle-rear side.

The engine 1 is coupled with a transmission 11 located on one sidethereof in the cylinder arrangement direction (in the first embodiment,on a vehicle-left side (left side in FIG. 1)). A combination of theengine 1 and the transmission 11 makes up a power plant 12. Thetransmission 11 is a transverse type having a non-illustrated inputshaft and a non-illustrated output shaft each extending in thevehicle-widthwise direction. The input shaft is coupled to a crankshaftof the engine 1 extending in the vehicle-widthwise direction, and theoutput shaft is coupled to a differential gear mechanism 14 disposed onthe vehicle-rear side of the transmission 11. Although not illustrated,right and left front wheel drive axles each coupled to a correspondingone of right and left front wheels extend from the differential gearmechanism 14 toward respective ones of opposite sides of thevehicle-widthwise direction. The vehicle is an FF (front engine, frontwheel drive) vehicle in which the right and left front wheels are drivenby the engine 1. It is understood that the vehicle may be afour-wheel-drive vehicle.

A left side frame 21 and a right side frame 22 are provided onrespective ones of opposite sides of the power plant 12 in thevehicle-widthwise direction.

Specifically, the left side frame 21 and the right side frame 22 aredisposed on a left side close to the transmission 11 and on a right sideclose to the engine 1, respectively, to extend in an frontward-rearwarddirection of the vehicle (vehicle-longitudinal direction).

A vehicle-rear-side wall of the engine compartment 19 is made up of adash panel 23 partitioning between the engine compartment 19 and apassenger compartment 20. The dash panel 23 extends in anupward-downward direction and in the vehicle-widthwise direction. Anupper end of the dash panel 23 is joined to a cowl member 24, and alower end of the dash panel 23 is joined to a front end of a floor panel25 defining a floor surface of the passenger compartment 20.

The floor panel 25 has a tunnel portion 25 a formed in avehicle-widthwise central region thereof to bulge upwardly in across-sectionally generally inverted-U shape and extend in thevehicle-longitudinal direction. The dash panel 23 has a tunnel opening23 a which is a upwardly-extending cutout formed in a vehicle-widthwisecentral region of the lower end thereof to communicate with the tunnelportion 25 a. Thus, a single exhaust pipe (after-mentioned downstreamexhaust pipe 51) will pass through an inner space of the tunnel portion25 a (outside of the passenger compartment 20). When the vehicle is afour-wheel-drive vehicle, an exhaust pipe and a drive shaft for drivingrear wheels will pass through the inner space of the tunnel portion 25a.

An intake manifold 4 is provided on a vehicle-front side of the engine 1to introduce intake air into each of the cylinders 2 of the engine 1.The intake manifold 4 has four branch pipe portions 4 a, 4 b, 4 c, 4 deach connected to a respective one of four intake ports (not shown)which are communicated with respective ones of the four cylinders 2 ofthe engine 1 and opened on a vehicle-front-side surface of the engine 1.The branch pipe portions 4 a to 4 d are curvedly formed to surround asurge tank 5 extending in the cylinder arrangement direction(vehicle-widthwise direction).

The exhaust apparatus E is provided on the vehicle-rear side of theengine 1 to discharge exhaust gas produced in each of the cylinders 2 ofthe engine 1. With reference to FIGS. 3 to 5, details of the exhaustapparatus E will be specifically described below.

The exhaust apparatus E comprises an exhaust manifold 31, a manifoldcatalytic converter 40 as a unit for purifying exhaust gas of the engine1 (exhaust gas-purifying unit), and a downstream exhaust pipe 51, whichare arranged in this order from an exhaust upstream side (upstream sideof an exhaust gas stream). A combination of the exhaust manifold 31 andthe manifold catalytic converter 40 makes up an upstream exhaustassembly 48 of the exhaust apparatus E. The upstream exhaust assembly 48is housed in the engine compartment 19.

The exhaust manifold 31 includes four branch pipe portions 32communicated with respective ones of the four cylinders 2 of the engine1, two intermediate collector pipe portions 33 each formed by mergingtwo of the four branch pipe portions 32 together, and one single exhaustpipe portion 34 formed by merging the two intermediate collector pipeportions 33 together. The manifold catalytic converter 40 is connectedto an exhaust downstream end of the single exhaust pipe portion 34.

In the following description, the four cylinders 2 will be referred torespectively as “first cylinder 2 a”, “second cylinder 2 b”, “thirdcylinder 2 c” and “fourth cylinder 2 d”, in order from the side oppositeto the transmission 11 (vehicle-right side) toward the transmission 11(vehicle-left side). When it is not necessary to distinguish betweenthem in this manner, they will be referred to simply as “cylinders 2” ona case-by-case basis. Further, the branch pipe portions 32 communicatedwith respective ones of the first to fourth cylinders 2 a to 2 d will bereferred to respectively as “first branch pipe portion 32 a”, “secondbranch pipe portion 32 b”, “third branch pipe portion 32 c” and “forthbranch pipe portion 32 d”. When it is not necessary to distinguishbetween them in this manner, they will be referred to simply as “branchpipe portions 32” on a case-by-case basis.

An exhaust upstream end of each of the first to fourth branch pipeportions 32 a to 32 d is connected to a surface of the engine 1 on avehicle-rear side through a flange portion 36 provided to be shared byall of the branch pipe portions 32 a to 32 d and extending in thevehicle-widthwise direction. Specifically, the flange portion 36 isattached to the vehicle-rear-side surface of the engine 1 to allow theexhaust upstream ends of the first to fourth branch pipe portions 32 ato 32 d to be connected to respective ones of four exhaust ports (notshown) opened on the vehicle-rear-side surface of the engine 1, throughthe flange portion 36, so that the first to fourth branch pipe portions32 a to 32 d are communicated with respective ones of the first tofourth cylinders 2 a to 2 d.

The flange portion 36 has a plurality of (in the first embodiment, five)fastening points 37 each adapted to be fastened to the vehicle-rear-sidesurface of the engine 1 by a fastening member such as a bolt. Each ofthe fastening points 37 is formed as a through-hole for allowing thefastening member such as a bolt to be inserted thereinto. In thefollowing description, the five fastening points 37 will be referred torespectively as “first fastening point 37 a”, “second fastening point 37b”, “third fastening point 37 c”, “fourth fastening point 37 d” and“fifth fastening point 37 e”, in order from the vehicle-right side. Whenit is not necessary to distinguish between them in this manner, theywill be referred to simply as “fastening points 37” on a case-by-casebasis.

The first fastening point 37 a is provided in the flange portion 36 at aposition corresponding to a region on a vehicle-widthwise outer side(vehicle-right side) of the first cylinder 2 a. The second fasteningpoint 37 b is provided in the flange portion 36 at a positioncorresponding to a region between the first cylinder 2 a and the secondcylinder 2 b, and the third fastening point 37 c is provided in theflange portion 36 at a position corresponding to a region between thesecond cylinder 2 b and the third cylinder 2 c. The fourth fasteningpoint 37 d is provided in the flange portion 36 at a positioncorresponding to a region between the third cylinder 2 c and the fourthcylinder 2 d, and the fifth fastening point 37 e is provided in theflange portion 36 at a position corresponding to a region on avehicle-widthwise outer side (vehicle-left side) of the fourth cylinder2 d. The first to fifth fastening points 37 a to 37 e are arranged suchthat two lines each connecting a part of the fastening points extend inthe vehicle-widthwise direction (cylinder arrangement direction) inspaced-apart relation to each other in a heightwise direction. The upperfastening point line including the second and fourth fastening points 37b, 37 d is located at a first height position adjacent to an upper edgeof the flange portion 36, and the lower fastening point line includingthe first, third and fifth fastening points 37 a, 37 c, 37 e is locatedat a second height position adjacent to a lower edge of the flangeportion 36. Thus, each of the second and fourth fastening points 37 b,37 d corresponds to a high-position fastening point provided at thefirst height position, and each of the first, third and fifth fasteningpoints 37 a, 37 c, 37 e corresponds to a low-position fastening pointprovided at the second height position below the first height position.Further, the first to fifth fastening points 37 a to 37 e are arrangedin a zigzag pattern to allow each of the fastening points 37 on theupper line to be located in a corresponding one of two regions betweenadjacent ones of the fastening points 37 on the lower line.

Each of the intermediate collector pipe portions 33 is formed bydividing the four cylinders 2 into two cylinder groups each consistingof two cylinders 2 whose exhaust strokes (expansion strokes) are notsuccessive with respect to each other, and merging the branch pipeportions 32 communicated with respective ones of the two cylinders 2 ineach of the cylinder groups, on a cylinder group-by-cylinder groupbasis. In the first embodiment, the exhaust stroke occurs in thefollowing order: the first cylinder 2 a→the third cylinder 2 c→thefourth cylinder 2 d→the second cylinder 2 b. Thus, the four cylinders 2are divided into a cylinder group consisting of the first cylinder 2 aand the fourth cylinder 2 d, and a cylinder group consisting of thesecond cylinder 2 b and the third cylinder 2 c. Then, the first andfourth branch pipe portions 32 a, 32 d communicated with respective onesof the first and fourth cylinders 2 a, 2 d are merged together to formone of the intermediate collector pipe portions 33, and the second andthird branch pipe portions 32 b, 32 c communicated with respective onesof the second and third cylinders 2 b, 2 c are merged together to formthe other intermediate collector pipe portion 33. In the followingdescription, the intermediate collector pipe portion 33 formed bymerging the first and fourth branch pipe portions 32 a, 32 d togetherwill be referred to as “first intermediate collector pipe portion 33 a”,and the intermediate collector pipe portion 33 formed by merging thesecond and third branch pipe portions 32 b, 32 c together will bereferred to as “second intermediate collector pipe portion 33 b” When itis not necessary to distinguish between them in this manner, they willbe referred to simply as “intermediate collector pipe portions 33” on acase-by-case basis.

Each of the first to fourth branch pipe portions 32 a to 32 d extendsfrom the vehicle-rear-side surface of the engine 1 (in a strict sense,from the flange portion 36), basically toward the vehicle-rear side.More specifically, in top plan view, the first branch pipe portion 32 aextends from the vehicle-rear-side surface of the engine 1 toward thevehicle-rear side, and then extends obliquely toward the vehicle-rearside with an inclination toward the vehicle-left side. In top plan view,the fourth branch pipe portion 32 d extends from the vehicle-rear-sidesurface of the engine 1 toward the vehicle-rear side, and then extendsobliquely toward the vehicle-rear side with an inclination toward thevehicle-right side. Then, the first branch pipe portion 32 a and thefourth branch pipe portion 32 d are merged together at approximately thesame vehicle-widthwise position as that of the third fastening point 37c, and the first intermediate collector pipe portion 33 a is formed onan exhaust downstream side of the merging position. Further, in top planview, the second branch pipe portion 32 b extends from thevehicle-rear-side surface of the engine 1 toward the vehicle-rear side,and then extends obliquely toward the vehicle-rear side with aninclination toward the vehicle-right side. Then, just before the secondintermediate collector pipe portion 33 b, the second branch pipe portion32 b curves toward the opposite side and extends obliquely toward thevehicle-rear side with an inclination toward the vehicle-left side. Intop plan view, the third branch pipe portion 32 c extends from thevehicle-rear-side surface of the engine 1 toward the vehicle-rear side,and then extends obliquely toward the vehicle-rear side with aninclination toward the vehicle-right side. Then, the second branch pipeportion 32 b and the third branch pipe portion 32 c are merged togetherat approximately the same vehicle-widthwise position as that of thesecond fastening point 37 b, and the second intermediate collector pipeportion 33 b is formed on the exhaust downstream side of the mergingposition. Each of the second and third branch pipe portions 32 b, 32 cextends from the vehicle-left side toward the vehicle-right side of thefirst branch pipe portion 32 a, while passing across a region just belowthe first branch pipe portion 32 a.

In the first embodiment, respective exhaust upstream ends of the firstand second intermediate collector pipe portions 33 a, 33 b (the mergingposition of the first and fourth branch pipe portions 32 a, 32 d, andthe merging position of the second and third branch pipe portions 32 b,32 c) are disposed offset with respect to each other in thevehicle-widthwise direction. Specifically, an exhaust upstream end ofthe first intermediate collector pipe portion 33 a (the merging positionof the first and fourth branch pipe portions 32 a, 32 d) is located onthe vehicle-left side of (on the side of the transmission 11 withrespect to) an exhaust upstream end of the second intermediate collectorpipe portion 33 b (the merging position of the second and third branchpipe portions 32 b, 32 c). A height position of the exhaust upstream endof the first intermediate collector pipe portion 33 a is approximatelyequal to a height position of the exhaust upstream end of the secondintermediate collector pipe portion 33 b (in a strict sense, slightlyabove a height position of the exhaust upstream end of the secondintermediate collector pipe portion 33 b), and located below the thirdfastening point 37 c. This arrangement makes it possible to keep an areaaround each of the fastening points 37 (particularly, the thirdfastening point 37 c) of the flange portion 36 and a region just abovethe area from overlapping the branch pipe portions 32 and theintermediate collector pipe portions 33, when viewed from thevehicle-rear side, as shown in FIG. 5. Thus, a space for a fasteningoperation at each of the fastening points 37 (particularly, the thirdfastening point 37 c) can be ensured to allow a fastening member to beset in each area around the fastening points 37 from above the engine 1,which makes it easy to perform the fastening operation.

The first and second intermediate collector pipe portions 33 a, 33 b aremerged together while curving to allow respective exhaust downstreamregions of the first and second intermediate collector pipe portions 33a, 33 b to be oriented toward one side of the vehicle-widthwisedirection (in the first embodiment, toward the vehicle-left side, i.e.,toward the transmission 11), in top plan view, and the single exhaustpipe portion 34 is formed on the exhaust downstream side of the mergingposition of the first and second intermediate collector pipe portions 33a, 33 b. Specifically, the first intermediate collector pipe portion 33a extends from the exhaust upstream end thereof toward the vehicle-rearside, and then curves toward the vehicle-left side, and the secondintermediate collector pipe portion 33 b curves toward the vehicle-leftside directly from the exhaust upstream end thereof, and extends towardthe vehicle-left side while passing across a region just below theexhaust upstream end of the first intermediate collector pipe portion 33a. Then, the first and second intermediate collector pipe portions 33 a,33 b are merged together at approximately the same position as that ofthe fourth cylinder in the vehicle-widthwise direction (at a portionnear a vehicle-widthwise central region of the engine compartment 19) toform the single exhaust pipe portion 34. In this manner, the singleexhaust pipe portion 34 is provided on the exhaust downstream side ofthe branch pipe portions 32, and communicated with the four branch pipeportions 32 a to 32 d via the first and second intermediate collectorpipe portions 33 a, 33 b.

The single exhaust pipe portion 34 is connected to the manifoldcatalytic converter 40 while curving to allow an exhaust downstreamregion of the single exhaust pipe portion 34 to be oriented toward thevehicle-front side, in top plan view. The exhaust downstream region ofthe single exhaust pipe portion 34 curves toward the vehicle-front sidewith an inclination toward the vehicle-right side, and the singleexhaust pipe portion 34 has an intermediate region formed in a curvedshape which is convexed toward a side opposite to the manifold catalyticconverter 40 (toward the vehicle-left side) with respect to both ends ofthe single exhaust pipe portion 34. The exhaust downstream end of thesingle exhaust pipe portion 34 is increased in diameter to have the samediameter as that of an after-mentioned casing 41 of the manifoldcatalytic converter 40, and connected to an exhaust upstream end surfaceof the casing 41 (a left end surface of the casing 41 on thevehicle-left side).

The manifold catalytic converter 40 is disposed on the vehicle-rear sideof the engine 1, and disposed to allow a gas passage inside the casing41 to extend approximately in the vehicle-widthwise direction, in topplan view. Thus, the casing 41 extends approximately along thevehicle-rear-side surface of the engine 1. In the first embodiment, in astrict sense, the casing 41 (gas passage) is inclined to be graduallyshifted toward the vehicle-rear side by a slight distance as goingtoward the vehicle-left side (exhaust upstream side). This is intendedto allow a gas entry angle with respect to an exhaust upstream endsurface 43 a of a catalyst installation portion 43 to be set as close aspossible to 90 degrees, as described later. Further, the casing 41 (gaspassage) is inclined to be gradually shifted downwardly by a slightdistance as going toward the vehicle-right side (exhaust downstreamside). This is because the downstream exhaust pipe 51 is located justbelow the second and third branch pipe portions 32 b, 32 c and thesecond intermediate collector pipe portion 33 b, i.e., intended to avoidinterference with these portions (32 b, 32 c, 33 b).

The manifold catalytic converter 40 is formed by installing a catalystin a gas passage inside an generally cylindrical-shaped casing 41. Acatalyst installation portion 43 in the gas passage inside the casing 41has a generally circular shape in cross-section. Each of an exhaustupstream end surface 43 a (vehicle-left-side end surface) and an exhaustdownstream end surface 43 b (vehicle-right-side end surface) of thecatalyst installation portion 43 is located in substantially the sameplane as that of a corresponding one of an exhaust upstream end surfaceand an exhaust downstream end surface of the casing 41, or locatedslightly inward of the casing 41. Although the catalyst is a three-waycatalyst, it is designed particularly to purify HC and CO during warm-upof the engine 1. For this purpose, the manifold catalytic converter 40is provided in the upstream exhaust assembly 48 of the exhaust apparatusE. It is understood that the cross-sectional shape of the catalystinstallation portion 43 is not limited to the generally circular shape.

In the first embodiment, the manifold catalytic converter 40 issupported with respect to the vehicle-rear-side surface of the engine 1.Specifically, a protruding member 41 a is fixed to the casing 41 toprotrude downwardly, and a support member 44 having a generallyinverted-L shape when viewed from thereabove is provided between theprotruding member 41 a and the vehicle-rear-side surface of the engine1, so that the manifold catalytic converter 40 is supported by thevehicle-rear-side surface of the engine 1 through the support member 44.The support of the manifold catalytic converter 40 with respect to theengine 1 is not indispensable.

The downstream exhaust pipe 51 is connected to the exhaust downstreamend surface (vehicle-right-side end surface) of the casing 41 of themanifold catalytic converter 41. The downstream exhaust pipe 51 isdisposed to extend from a connection portion thereof with the manifoldcatalytic converter 40 (exhaust upstream end thereof), toward the tunnelopening 23 a formed in the vehicle-widthwise central region of the lowerend of the dash panel 23. Specifically, in top plan view, the downstreamexhaust pipe 51 curves toward the vehicle-rear side at the exhaustupstream end thereof and extends toward the vehicle-rear side. Then, thedownstream exhaust pipe 51 extends obliquely toward the vehicle-rearside with an inclination toward the vehicle-left side (toward avehicle-widthwise central region of the engine compartment 19). Then,when the downstream exhaust pipe 51 reaches a position in front of thetunnel opening 23 a, it extends toward the vehicle-rear side, and entersthe tunnel portion 25 a from the tunnel opening 23 a. The downstreamexhaust pipe 51 is comprised of a plurality of divided pipe members 52formed by dividing the downstream exhaust pipe 51 into a plurality ofpieces along a length direction thereof. Adjacent two of the pipemembers 52 are connected together through two flanges 52 a formed atrespective connection ends of the adjacent pipe members 52. In FIGS. 1and 2, only an upstreammost one of the pipe members 52 and a part of thepipe member 52 located immediately on the exhaust downstream side of theupstreammost pipe member 52 are illustrated, and the illustration of theremaining pipe members 52 is omitted. Further, in FIGS. 3 to 5, only theupstreammost pipe member 52 is illustrated.

The exhaust downstream region of the single exhaust pipe portion 34protrudes toward the vehicle-left side with respect to the exhaustupstream end surface 43 a of the catalyst installation portion 43 of themanifold catalytic converter 40, and an exhaust upstream region of thedownstream exhaust pipe 51 protrudes toward the vehicle-right side withrespect to the exhaust downstream end surface 43 b of the catalystinstallation portion 43. Further, a maximum vehicle-widthwise protrudingamount of the single exhaust pipe portion 34 with respect to the exhaustupstream end surface 43 a of the catalyst installation portion 43 is setto be greater than a maximum vehicle-widthwise protruding amount of thedownstream exhaust pipe 51 with respect to the exhaust downstream endsurface 43 b of the catalyst installation portion 43, to allow a gasentry angle with respect to the exhaust upstream end surface 43 a of thecatalyst installation portion 43 (the gas entry angle means an acute oneof two angles defined between a flow direction of exhaust gas enteringthe catalyst installation portion 43 from the single exhaust pipeportion 34 and the exhaust upstream end surface 43 a of the catalystinstallation portion 43) to become greater than a gas discharge anglewith respect to the exhaust downstream end surface 43 b of the catalystinstallation portion 43 (the gas discharge angle means an acute one oftwo angles defined between the exhaust downstream end surface 43 b ofthe catalyst installation portion 43 and a flow direction of exhaust gasdischarged from the catalyst installation portion 43 to the downstreamexhaust pipe 51) (i.e., to allow the gas entry angle to become closer to90 degree as compared with the gas discharge angle). Specifically, theexhaust downstream region of the single exhaust pipe portion 34 isconfigured to reduce an inclination with respect to an extensiondirection of the casing 41 (catalyst installation portion 43) andlargely extend in the extension direction of the casing 41 (catalystinstallation portion 43), as compared with the exhaust upstream regionof the downstream exhaust pipe 51, to allow the gas entry angle withrespect to the exhaust upstream end surface 43 a of the catalystinstallation portion 43 to be set as close as possible to 90 degrees soas to cause exhaust gas entering the catalyst installation portion 43 tobe uniformly dispersed over the entire cross-section of the catalystinstallation portion 43.

The upstreammost pipe member 52 of the downstream exhaust pipe 51 has aflexible joint 53. The flexible joint 53 is located inside the tunnelportion 25 a, and designed to absorb vibration of the engine 1 andvibration of the upstream exhaust assembly 48 caused by the vibration ofthe engine 1 so as to prevent the vibrations from being transmitted to aregion on the exhaust downstream side of the flexible joint 53. Thenumber of the flexible joints 53 is not limited to one, but a pluralityof the flexible joints 53 may be provided in series at intervals alongthe length direction of the downstream exhaust pipe 51 (seeafter-mentioned third and fourth embodiments).

The upstreammost pipe member 52 is supported with respect to a vehiclebody (floor panel 25) of the vehicle through a portion thereof locatedon the exhaust downstream side of the flexible joint 53. Specifically,an elongate rod-shaped support member 55 is bent into a generallytrapezoidal shape, in top plan view. An upper side of thetrapezoidal-shaped support member 55 is fixed to a vicinity of theflange 52 a of the upstreammost pipe member 52. Each of opposite ends ofa lower side of the trapezoidal-shaped support member 55 is formed toprotrude outwardly in the vehicle-widthwise direction, and a distal endof each of the protruding portions is attached to the floor panel 25through an elastic member 56. In cases where a plurality of the flexiblejoints 53 are provided in the upstreammost pipe member 52, theupstreammost pipe member 52 may be supported with respect to the vehiclebody through a portion thereof located on the exhaust downstream side ofa downstreammost one of the flexible joints 53.

The pipe member 52 immediately on the exhaust downstream side of theupstreammost pipe member 52 is provided with an underfoot catalyticconverter 60 having a structure similar to that of the manifoldcatalytic converter 40. Although a catalyst of the underfoot catalyticconverter 60 is a three-way catalyst as with the manifold catalyticconverter 40, it is designed to primarily purify NOx. The pipe member 52provided with the underfoot catalytic converter 60 is supported withrespect to the vehicle body (floor panel 25) by a support structuresimilar to that for the upstreammost pipe member 52.

In the first embodiment, the branch pipe portions 32, the intermediatecollector pipe portions 33, the single exhaust pipe portion 34 and themanifold catalytic converter 40 which constitute the upstream exhaustassembly 48 of the exhaust apparatus E are formed in a loop shapeturning in a clockwise direction toward the exhaust downstream side, intop plan view, so that the upstream exhaust assembly 48 including themanifold catalytic converter 40 can be compactly laid out on thevehicle-rear side of the engine 1, while increasing a length of each ofthe branch pipe portions 32 and the intermediate collector pipe portions33 to enhance exhaust efficiency. In addition, each of the intermediatecollector pipe portions 33 curves to allow the exhaust downstream regionthereof to be oriented toward one side of the vehicle-widthwisedirection (vehicle-left side) which is a direction coming close to thetransmission 11, in top plan view, so that the single exhaust pipeportion 34 is disposed at a position closer to the transmission 11 thanthe branch pipe portions 32. Thus, the upstream exhaust assembly 48 canbe disposed away from auxiliary components (water pump, etc.) which aregenerally disposed on a surface of the engine 1 on an opposite side ofthe transmission 11, and a vehicle-right-side sidewall of the enginecompartment 19 (the side frame, etc.). The makes it possible to achievea layout advantageous in terms of space utility, without interferencewith the auxiliary components, the side frame, etc., and suppress aninfluence of radiant heat on the auxiliary components and thevehicle-right-side sidewall of the engine compartment 19. Further, evenif the length of each of the branch pipe portions 32 and theintermediate collector pipe portions 33 is increased, the tunnel portion25 a is required to allow only the single downstream exhaust pipe 51 topass therethrough, so that there is no need to increase across-sectional area of the tunnel portion 25 a, which makes it possibleto prevent a space of the passenger compartment 20 from being narrowed.

In this case, there is a possibility that the upstream exhaust assembly48 formed in a loop shape brings an disadvantage in terms of exhaustresistance, as compared with a straight shape. However, a diameter ofthe loop can be set to a relatively large value by laying out theupstream exhaust assembly 48 in the above manner. Thus, a problem of theexhaust resistance practically does not occur, but it becomes possibleto increase an output power of the engine 1 based on the exhaustefficiency-enhancing effect obtained by increasing the length of each ofthe branch pipe portions 32 and the intermediate collector pipe portions33.

Further, the manifold catalytic converter 40 is disposed adjacent to thevehicle-rear-side surface of the engine 1, so that a traveling windproduced by traveling of the vehicle becomes less likely to touch themanifold catalytic converter 40, which makes it possible to more quicklyraise a temperature of the catalyst of the manifold catalytic converter40 during warm-up of the engine 1.

Furthermore, the manifold catalytic converter 40 is disposed on thevehicle-front side of a connection position of each of the intermediatecollector pipe portions 33 and the single exhaust pipe portion 34 (theexhaust upstream end of the single exhaust pipe portion 34) and belowthe branch pipe portions 32. Thus, the manifold catalytic converter 40having a large weight is disposed adjacent to the engine 1, so thatvibration of the upstream exhaust assembly 48 to be caused by vibrationof the engine 1 can be reduced, as compared with an arrangement wherethe manifold catalytic converter 40 is disposed away from the engine 1.In the first embodiment, the manifold catalytic converter 40 issupported with respect to the vehicle-rear-side surface of the engine 1,so that the upstream exhaust assembly 48 can be stably supported tofurther reduce the vibration of the upstream exhaust assembly 48 to becaused by the vibration of the engine 1.

In addition, the exhaust upstream ends of the first and secondintermediate collector pipe portions 33 a, 33 b are disposed offset withrespect to each other in the vehicle-widthwise direction, so that itbecomes possible to keep the branch pipe portions 32 from being locatedjust above the exhaust upstream ends of the first and secondintermediate collector pipe portions 33 a, 33 b. Further, the exhaustupstream end of the single exhaust pipe portion 34 (the merging positionof the first and second intermediate collector pipe portions 33 a, 33 b)is also disposed offset with respect to the exhaust upstream ends of thefirst and second intermediate collector pipe portions 33 a, 33 b in thevehicle-widthwise direction, so that any component of the exhaustapparatus E is not located just above all of the exhaust upstream ends.Thus, welding between corresponding ones of the branch pipe portions 32and the intermediate collector pipe portions 33, and welding betweeneach of the intermediate collector pipe portions 33 and the singleexhaust pipe portion 34, can be performed all together so as to increaseproductivity.

Second Embodiment

FIGS. 6 to 8 show an exhaust apparatus E according to a secondembodiment of the present invention, wherein a positional relationshipbetween respective exhaust upstream ends of first and secondintermediate collector pipe portions 33 a, 33 b (a merging position offirst and fourth branch pipe portions 32 a, 32 d, and a merging positionof second and third branch pipe portions 32 b, 32 c) is defineddifferently from that in the first embodiment.

Specifically, in the second embodiment, the exhaust upstream ends of thefirst and second intermediate collector pipe portions 33 a, 33 b aredisposed at approximately the same position as that of a third fasteningpoint 37 c of a flange portion 36 in the vehicle-widthwise direction,and in offset relation to each other in an upward-downward direction.More specifically, the first branch pipe portion 32 a and the fourthbranch portion 32 d are merged in the same manner as that in the firstembodiment, whereas the second branch pipe portion 32 b and the thirdbranch portion 32 c extend from the vehicle-rear-side surface of theengine 1 toward the vehicle-rear side, and then come close to each otherso that they are merged together at approximately the same position asthat of the third fastening point 37 c in the vehicle-widthwisedirection. Further, the exhaust upstream end of the first intermediatecollector pipe portion 33 a is located just below the exhaust upstreamend of the second intermediate collector pipe portion 33 b, i.e., theexhaust upstream ends of the first and second intermediate collectorpipe portions 33 a, 33 b overlap each other, in top plan view. A heightposition of the exhaust upstream end of the first intermediate collectorpipe portion 33 a is located below the third fastening point 37 c aswith the first embodiment, whereas a height position of the exhaustupstream end of the second intermediate collector pipe portion 33 b islocated above the third fastening point 37 c. This makes it possible tokeep an area around the third fastening point 37 c of the flange portion36 from overlapping the branch pipe portions 32 and the intermediatecollector pipe portions 33, when viewed from the vehicle-rear side, asshown in FIG. 8. Thus, the fastening operation at the third fasteningpoint 37 c can be performed from the vehicle-rear side. However, aregion just above the area around the third fastening point 37 c of theflange portion 36 overlaps the third branch pipe portion 32 c whenviewed from the vehicle-rear side, and thereby it becomes difficult toperform an operation of setting a fastening member in the area aroundthe third fastening point 37 c from above the engine 1. Thus, efficiencyof the fastening operation is slightly inferior to that in the firstembodiment. On the other hand, an area around each of the remainingfastening points 37 (37 a, 37 b, 37 d, 37 e) of the flange portion 36other than the third fastening point 37 c and a region just above thearea do not overlap the branch pipe portions 32 and the intermediatecollector pipe portions 33 when viewed from the vehicle-rear side. Thus,the fastening operation at each of the remaining fastening points 37other than the third fastening point 37 c can be performed with the sameefficiency as that in the first embodiment.

The first and second intermediate collector pipe portions 33 a, 33 b aremerged together while curving to allow respective exhaust downstreamregions of the first and second intermediate collector pipe portions 33a, 33 b to be oriented toward one side of the vehicle-widthwisedirection (toward the vehicle-left side, i.e., toward the transmission11), in top plan view. Specifically, the first and second intermediatecollector pipe portions 33 a, 33 b extend from the respective exhaustupstream ends thereof toward the vehicle-rear side and then curve andextend toward the vehicle-left side, in overlapping relation to eachother, in top plan view. Then, the first and second intermediatecollector pipe portions 33 a, 33 b are merged together at approximatelythe same position as that of the fourth cylinder 2 d in thevehicle-widthwise direction, and a single exhaust pipe portion 34 isformed on the exhaust downstream side of the merging position.

A configuration and an arrangement of each of a power plant 12, thesingle exhaust pipe portion 34, a manifold catalytic converter 40 and adownstream exhaust pipe 51 are the same as those in the firstembodiment. By way of exception, in the second embodiment, a casing 41(gas passage) is not inclined toward the vehicle-rear side as goingtoward the vehicle-left side, differently from the first embodiment.This is because a maximum vehicle-widthwise protruding amount of thesingle exhaust pipe portion 34 with respect to an exhaust upstream endsurface 43 a of a catalyst installation portion 43 is set to a valuegreater than that in the first embodiment, and thereby the gas entryangle with respect to the exhaust upstream end surface 43 a of thecatalyst installation portion 43 can be set as close as possible to 90degrees without inclining the casing 41 toward the vehicle-rear side asgoing toward the vehicle-left side.

As above, in the second embodiment, the branch pipe portions 32, theintermediate collector pipe portions 33, the single exhaust pipe portion34 and the manifold catalytic converter 40 which constitute an upstreamexhaust assembly 48 of the exhaust apparatus E are formed in a loopshape, in top plan view, and each of the intermediate collector pipeportions 33 curves to allow the exhaust downstream region thereof to beoriented toward one side of the vehicle-widthwise direction (toward thevehicle-left side) which is a direction coming close to the transmission11, in top plan view, as with the first embodiment, so that the samefunctions/effects as those in the first embodiment can be obtained.

In addition, the exhaust upstream ends of the first and secondintermediate collector pipe portions 33 a, 33 b overlap each other, intop plan view, so that respective curvature radii of the first andsecond intermediate collector pipe portions 33 a, 33 b can be set toapproximately the same and relatively large values, by effectivelyutilizing a space in an upward-downward direction.

Third Embodiment

FIGS. 9 to 11 show an exhaust apparatus E according to a thirdembodiment of the present invention, wherein a positional relationshipbetween respective exhaust upstream ends of first and secondintermediate collector pipe portions 33 a, 33 b (a merging position offirst and fourth branch pipe portions 32 a, 32 d, and a merging positionof second and third branch pipe portions 32 b, 32 c) is defineddifferently from those in the first and second embodiments.

Specifically, in the third embodiment, the exhaust upstream ends of thefirst and second intermediate collector pipe portions 33 a, 33 b aredisposed at approximately the same position as that of a third fasteningpoint 37 c of a flange portion 36 in the vehicle-widthwise direction, aswith the second embodiment. However, the exhaust upstream ends of thefirst and second intermediate collector pipe portions 33 a, 33 b areoffset with respect to each other in the vehicle-longitudinal direction,instead of overlapping each other, in top plan view. More specifically,a length of each of the second and third branch pipe portions 32 b, 32 cin the vehicle-longitudinal direction is set to be greater than a lengthof each of the first and fourth branch pipe portions 32 a, 32 d in thevehicle-longitudinal direction, and the exhaust upstream end of thesecond intermediate collector pipe portion 33 b (the merging position ofthe second and third branch pipe portions 32 b, 32 c) is located on thevehicle-rear side of the exhaust upstream end of the first intermediatecollector pipe portion 33 a (the merging position of the first andfourth branch pipe portions 32 a, 32 d). Further, a height position ofthe exhaust upstream end of the second intermediate collector pipeportion 33 b is approximately equal to a height position of the exhaustupstream end of the first intermediate collector pipe portion 33 a, andlocated below the third fastening point 37 c. This makes it possible tokeep an area around the third fastening point 37 c of the flange portion36 and a region just above the area from overlapping the branch pipeportions 32 and the intermediate collector pipe portions 33, as well asthe remaining fastening points 37 (37 a, 37 b, 37 d, 37 e), when viewedfrom the vehicle-rear side, as shown in FIG. 11.

Alternatively, the height position of the exhaust upstream end of thesecond intermediate collector pipe portion 33 b may be set in the samemanner as that in the second embodiment, i.e., may be set to be locatedabove the third fastening point 37 c. Even in this case, there is apossibility of being able to efficiently perform the operation ofsetting a fastening member in the area around the third fastening point37 c from above the engine 1, because the exhaust upstream end of thesecond intermediate collector pipe portion 33 b is located furthertoward the vehicle-rear side, as compared with the second embodiment.However, in view of enhancing the efficiency of the fastening operation,it is basically more preferable that the exhaust upstream end of thesecond intermediate collector pipe portion 33 b is set at a positionbelow the third fastening point 37 c.

The first and second intermediate collector pipe portions 33 a, 33 b aremerged together while curving to allow respective exhaust downstreamregions of the first and second intermediate collector pipe portions 33a, 33 b to be oriented toward one side of the vehicle-widthwisedirection (toward the vehicle-left side, i.e., toward the transmission11), in top plan view. Specifically, the first intermediate collectorpipe portion 33 a extends from the exhaust upstream end thereof towardthe vehicle-rear side. Then, the first intermediate collector pipeportion 33 a curves toward the vehicle-left side at a position justbelow the exhaust upstream end of the second intermediate collector pipeportion 33 b, and extends toward the vehicle-left side. The secondintermediate collector pipe portion 33 b curves toward the vehicle-leftside directly from the exhaust upstream end thereof, and extends towardthe vehicle-left side while passing through a region on the vehicle-rearside of the first intermediate collector pipe portion 33 a. Then, thefirst and second intermediate collector pipe portions 33 a, 33 b aremerged together at approximately the same position as that of the fourthcylinder 2 d in the vehicle-widthwise direction, to form a singleexhaust pipe portion 34.

A configuration and an arrangement of each of a power plant 12, thesingle exhaust pipe portion 34 and a manifold catalytic converter 40 arethe same as those in the first or second embodiment.

In the third embodiment, a downstream exhaust pipe 51 curves toward thevehicle-rear side at an exhaust upstream end thereof. Then, thedownstream exhaust pipe 51 extends obliquely toward the vehicle-rearside with an inclination toward the vehicle-left side (toward thevehicle-widthwise central region of the engine compartment 19), andenters the tunnel portion 25 a while maintaining the inclination. Then,the downstream exhaust pipe 51 is disposed to pass through a region ofthe tunnel portion 25 a on the vehicle-right side. Further, a supportmember 55 and an elastic member 56 are provided only on thevehicle-right side of the downstream exhaust pipe 51. The abovearrangement is intended to ensure a space (on the vehicle-left side) forallowing a drive shaft for driving rear wheels to pass therethrough, soas to make it possible to promptly change over to the vehicle into afour-wheel-drive vehicle, even if it is an FF vehicle. Thus, in thechangeover to a four-wheel-drive vehicle, the drive shaft can beprovided without modifying the downstream exhaust pipe 51, the supportmember 55, etc.

In the third embodiment, an upstreammost one of a plurality of dividedpipe members 52 of the downstream exhaust pipe 51 has two flexiblejoints 53 arranged in series at intervals along a length direction ofthe downstream exhaust pipe 51 (upstreammost pipe member 52). An exhaustdownstream one of the flexible joints 53 is disposed inside the tunnelportion 25 a, whereas the other of exhaust upstream flexible joint 53 isdisposed inside the engine compartment 19.

As above, in the third embodiment, the branch pipe portions 32, theintermediate collector pipe portions 33, the single exhaust pipe portion34 and the manifold catalytic converter 40 which constitute an upstreamexhaust assembly 48 of the exhaust apparatus E are formed in a loopshape, in top plan view, and each of the intermediate collector pipeportions 33 curves to allow the exhaust downstream region thereof to beoriented toward one side of the vehicle-widthwise direction (toward thevehicle-left side) which is a direction coming close to the transmission11, in top plan view, as with the first embodiment, so that the samefunctions/effects as those in the first embodiment can be obtained.

Fourth Embodiment

FIGS. 12 to 14 show an exhaust apparatus E according to a fourthembodiment of the present invention, wherein an exhaust manifold 31 isconfigured such that the intermediate collector pipe portions 33 of inthe first to third embodiments are eliminated, and four branch pipeportions 32 a, 32 b, 32 c, 32 d are merged together to form a singleexhaust pipe portion 34.

Specifically, differently from the first to third embodiments 1 to 3where a section of the upstream exhaust assembly 48 on the exhaustupstream side of the single exhaust pipe portion 34 is comprised of thebranch pipe portions 32 and the intermediate collector pipe portions 33,the section in the fourth embodiment is comprised only of the branchpipe portions 32. The single exhaust pipe portion 34 is formed bymerging the four branch pipe portions 32 a to 32 d together, anddirectly communicated with the branch pipe portions 32 without anintermediary of the intermediate collector pipe portions 33. Each of thebranch pipe portions 32 curves to allow an exhaust downstream region ofthe branch pipe portion 32 to be oriented toward one side of thevehicle-widthwise direction (toward the vehicle-left side, i.e., towardthe transmission 11), in top plan view. Specifically, each of the firstand second branch pipe portions 32 a, 32 b extends from thevehicle-rear-side surface of the engine 1 toward the vehicle-rear side,and then curves to allow the exhaust downstream region thereof to oneside of the vehicle-widthwise direction (toward the vehicle-left side,i.e., toward the transmission 11), in top plan view. Further, each ofthe third and fourth branch pipe portions 32 c, 32 d extends from thevehicle-rear-side surface of the engine 1 toward the vehicle-rear side,and, shortly thereafter, extends obliquely toward the vehicle-rear sidewith an inclination toward the vehicle-right side. Then, each of thethird and fourth branch pipe portions 32 c, 32 d curves toward one sideof the vehicle-widthwise direction (toward the vehicle-left side, i.e.,toward the transmission 11). Then, the four branch pipe portions 32 a to32 d are merged together at an approximately the same vehicle-widthwiseposition as that of a fifth fastening point 37 e of a flange portion 36to form a single exhaust pipe portion 34.

A configuration and an arrangement of each of a power plant 12, thesingle exhaust pipe portion 34, a manifold catalytic converter 40 and adownstream exhaust pipe 51 are the same as those in the thirdembodiment.

Thus, in the fourth embodiment, the branch pipe portions 32, the singleexhaust pipe portion 34 and the manifold catalytic converter 40 whichconstitute an upstream exhaust assembly 48 of the exhaust apparatus Eare formed in a loop shape, in top plan view, and each of the branchpipe portions 32 curves to allow the exhaust downstream region thereofto be oriented toward one side of the vehicle-widthwise direction(toward the vehicle-left side) which is a direction coming close to thetransmission 11, in top plan view, as with the first embodiment, so thatthe same functions/effects as those in the first embodiment can beobtained.

Although each of the first to fourth embodiments has been described bytaking an exhaust apparatus E for an inline four-cylinder engine 1 as anexample, the number of cylinders of the engine 1 is not limited to four.For example, in an exhaust apparatus devoid of the intermediatecollector pipe portions 33, the number of cylinders may be two or more.Further, in an exhaust apparatus provided with the intermediatecollector pipe portions 33, the number of cylinders may be four or more.In an exhaust apparatus provided with the intermediate collector pipeportions 33, depending on the number of cylinders of the engine 1, thenumber of the intermediate collector pipe portions 33 (i.e., the numberof the cylinder groups) may be increased to three or more, and thenumber of the branch pipe portions 32 to be merged to form one of theintermediate collector pipe portions 33 (i.e., the number of cylinderscomprised in one of the cylinder groups) may be increased to three ormore.

At the last of the description, features of the present inventiondisclosed based on the above embodiments and advantages thereof will besummarized.

The present invention is directed to an exhaust apparatus provided in anengine having a plurality of cylinders arranged in a line, wherein theengine is transversely placed in an engine compartment at a front of avehicle to allow a cylinder arrangement direction to be oriented in avehicle-widthwise direction, and coupled with a transmission located onone side thereof in the cylinder arrangement direction. The exhaustapparatus comprises an upstream exhaust assembly connected to a surfaceof the engine on a vehicle-rear side, and a downstream exhaust pipeprovided on an exhaust downstream side of the upstream exhaust assembly.The upstream exhaust assembly includes: a plurality of branch pipeportions communicated with respective ones of the plurality of cylindersand extending from the vehicle-rear-side surface of the engine towardthe vehicle-rear side; a single exhaust pipe portion provided on theexhaust downstream side of the plurality of branch pipe portions in sucha manner that it is communicated with the branch pipe portions; and anexhaust gas-purifying unit connected to an exhaust downstream end of thesingle exhaust pipe portion. The exhaust gas-purifying unit is disposedon the vehicle-rear side of the engine to allow a gas passagethereinside to extend approximately in the vehicle-widthwise direction,in top plan view. The upstream exhaust assembly includes, on an exhaustupstream side of the single exhaust pipe portion, a section which curvesto allow an exhaust downstream region of the section to be orientedtoward one side of the vehicle-widthwise direction which is a directioncoming close to the transmission, in top plan view, and the singleexhaust pipe portion curves to allow an exhaust downstream region of thesingle exhaust pipe portion to be oriented toward a vehicle-front side,in top plan view. The downstream exhaust pipe is connected to an exhaustdownstream end of the exhaust gas-purifying unit, and disposed to extendfrom a connection portion thereof with the exhaust gas-purifying unittoward an tunnel opening formed in a vehicle-widthwise central region ofa lower end of a dash panel of the vehicle.

In the exhaust apparatus of the present invention, a section of theupstream exhaust assembly extending from the branch pipe portions to theexhaust gas-purifying unit is formed in a loop shape, in top plan view,so that the upstream exhaust assembly including the exhaustgas-purifying unit can be compactly laid out on the vehicle-rear side ofthe engine, while increasing a length of each of the branch pipeportions (or each of the branch pipe portions and a plurality ofintermediate collector pipe portions) to enhance exhaust efficiency. Inaddition, the section of the upstream exhaust assembly on the exhaustupstream side of the single exhaust pipe portion (each of the branchpipe portion or the intermediate collector pipe portions) curves toallow the exhaust downstream region thereof to be oriented toward oneside of the vehicle-widthwise direction which is a direction comingclose to the transmission, in top plan view, so that the single exhaustpipe portion is disposed at a position closer to the transmission thanthe branch pipe portions. Thus, the upstream exhaust assembly can bedisposed away from auxiliary components (water pump, etc.) which aregenerally disposed on a surface of the engine 1 on an opposite side ofthe transmission, and a sidewall of the engine compartment (a sideframe, etc.). The makes it possible to achieve a layout advantageous interms of space utility, without interference with the auxiliarycomponents, the side frame, etc., and suppress an influence of radiantheat on the auxiliary components and the sidewall of the enginecompartment. Further, even if the length of each of the branch pipeportions (or each of the branch pipe portions and the intermediatecollector pipe portions) is increased, the tunnel portion is required toallow only the single downstream exhaust pipe to pass therethrough, sothat there is no need to increase a cross-sectional area of the tunnelportion.

In this case, there is a possibility that the upstream exhaust assemblyformed in a loop shape brings an disadvantage in terms of exhaustresistance, as compared with a straight shape. However, a diameter ofthe loop can be set to a relatively large value by laying out theupstream exhaust assembly in the above manner. Thus, a problem of theexhaust resistance practically does not occur, but it becomes possibleto increase an output power of the engine 1 based on the exhaustefficiency-enhancing effect obtained by increasing the length of each ofthe branch pipe portions (or each of the branch pipe portions and theintermediate collector pipe portions).

Further, the upstream exhaust assembly formed in a loop shape makes itpossible to distribute an elongation of the upstream exhaust assemblycaused by thermal expansion, over the entire loop, so as to preventdegradation of the upstream exhaust assembly due to stressconcentration.

Further, the exhaust gas-purifying unit can be disposed adjacent to thevehicle-rear-side surface of the engine, so that a traveling windproduced by traveling of the vehicle becomes less likely to touch theexhaust gas-purifying unit, which makes it possible to more quicklyraise a temperature of a catalyst in the exhaust gas-purifying unitduring warm-up of the engine.

Furthermore, the exhaust gas-purifying unit having a large weight isdisposed adjacent to the engine, so that vibration of the upstreamexhaust assembly to be caused by vibration of the engine can be reduced,as compared with an arrangement where the exhaust gas-purifying unit isdisposed away from the engine.

As above, the transverse engine exhaust apparatus of the presentinvention make it possible to compactly lay out the upstream exhaustassembly thereof including the exhaust gas-purifying unit, in the enginecompartment without sacrificing a passenger compartment space, andquickly raise a temperature of a catalyst in the exhaust gas-purifyingunit during engine warm-up. In addition, an elongation of the upstreamexhaust assembly caused by thermal expansion can be distributed, andvibration of the upstream exhaust assembly to be caused by vibration ofthe engine can be reduced. Further, an influence of radiant heat onauxiliary components and a sidewall of the engine compartment can besuppressed.

Preferably, the exhaust apparatus of the present invention, the exhaustgas-purifying unit has a catalyst installation portion formed in across-sectionally generally circular shape and provided in the gaspassage, and a maximum vehicle-widthwise protruding amount of the singleexhaust pipe portion with respect to an exhaust upstream end surface ofthe catalyst installation portion is set to be greater than a maximumvehicle-widthwise protruding amount of the downstream exhaust pipe withrespect to an exhaust downstream end surface of the catalystinstallation portion, to allow a gas entry angle with respect to theexhaust upstream end surface of the catalyst installation portion tobecome greater than a gas discharge angle with respect to the exhaustdownstream end surface of the catalyst installation portion.

According to this feature, exhaust gas entering the exhaust upstream endsurface of the catalyst installation portion becomes more likely to beuniformly dispersed over the entire cross-section of the catalystinstallation portion, to allow a catalyst of the exhaust gas-purifyingunit to more efficiently purify exhaust gas. Further, the exhaustupstream end surface (the connection portion with the single exhaustpipe portion) of the catalyst installation portion is located closer tothe transmission than the exhaust downstream end surface thereof, sothat components and members interferable with the single exhaust pipeportion can be limited to a relatively small member, which makes it easyto increase the maximum vehicle-widthwise protruding amount of thesingle exhaust pipe portion with respect to the exhaust upstream endsurface.

Preferably, in the exhaust apparatus of the present invention, theexhaust gas-purifying unit is disposed on the vehicle-front side of anexhaust upstream end of the single exhaust pipe portion and below thebranch pipe portions.

According to this feature, the exhaust gas-purifying unit can bedisposed closer to the engine, so that it becomes possible to furtherreduce vibration of the upstream exhaust assembly to be caused byvibration of the engine.

More preferably, in the above exhaust apparatus, the exhaustgas-purifying unit is supported with respect to the engine, and thedownstream exhaust pipe has a flexible joint interposed therein.

According to this feature, the upstream exhaust assembly including theexhaust gas-purifying unit can be stably supported to further reduce thevibration of the exhaust upstream section to be caused by the vibrationof the engine. Although a region of the exhaust apparatus upstream ofthe flexible joint vibrates together with the engine, the vibration isabsorbed by the flexible joint, so that it becomes possible to preventthe vibration from being transmitted to a region located on the exhaustdownstream side of the flexible joint (and typically fixed to a vehiclebody of the vehicle).

Preferably, in the exhaust apparatus of the present invention, theupstream exhaust assembly has a plurality of intermediate collector pipeportions between each of the plurality of branch pipe portions and thesingle exhaust pipe portion, wherein each of the intermediate collectorpipe portions is formed by dividing the plurality of cylinders into aplurality of cylinder groups each consisting of two or more cylinderswhose exhaust strokes are not successive with respect to each other, andmerging the branch pipe portions communicated with respective ones ofthe cylinders in each of the cylinder groups, on a cylindergroup-by-cylinder group basis, and wherein the single exhaust pipeportion is formed by merging the plurality of intermediate collectorpipe portions together, and each of the plurality of intermediatecollector pipe portions curves to allow an exhaust downstream region ofthe intermediate collector pipe portion to be oriented toward one sideof the vehicle-widthwise direction which is a direction coming close tothe transmission, in top plan view.

According to this feature, an optimal configuration for enhancingexhaust efficiency can be obtained.

Preferably, in the exhaust apparatus of the present invention, thesection of the upstream exhaust assembly on the exhaust upstream side ofthe single exhaust pipe portion is comprised of the branch pipeportions, wherein the single exhaust pipe portion is formed by mergingthe plurality of branch pipe portions together, and each of theplurality of branch pipe portions curves to allow an exhaust downstreamregion of the branch pipe portion to be oriented toward one side of thevehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.

According to this feature, it becomes possible to eliminate the use ofthe intermediate collector pipe portions so as to facilitate reductionin cost of the exhaust apparatus.

This application is based on Japanese Patent application No. 2009-274196filed in Japan Patent Office on Dec. 2, 2009, the contents of which arehereby incorporated by reference.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention hereinafterdefined, they should be construed as being included therein.

1. An exhaust apparatus provided in an engine having a plurality ofcylinders arranged in a line, wherein the engine is transversely placedin an engine compartment at a front of a vehicle to allow a cylinderarrangement direction to be oriented in a vehicle-widthwise direction,and coupled with a transmission located on one side thereof in thecylinder arrangement direction, the exhaust apparatus comprising anupstream exhaust assembly connected to a surface of the engine on avehicle-rear side, and a downstream exhaust pipe provided on an exhaustdownstream side of the upstream exhaust assembly, wherein the upstreamexhaust assembly includes: a plurality of branch pipe portionscommunicated with respective ones of the plurality of cylinders andextending from the vehicle-rear-side surface of the engine toward thevehicle-rear side; a single exhaust pipe portion provided on the exhaustdownstream side of the plurality of branch pipe portions in such amanner that it is communicated with the branch pipe portions; and anexhaust gas-purifying unit connected to an exhaust downstream end of thesingle exhaust pipe portion, and wherein: the exhaust gas-purifying unitis disposed on the vehicle-rear side of the engine to allow a gaspassage thereinside to extend approximately in the vehicle-widthwisedirection, in top plan view; the upstream exhaust assembly includes, onan exhaust upstream side of the single exhaust pipe portion, a sectionwhich curves to allow an exhaust downstream region of the section to beoriented toward one side of the vehicle-widthwise direction which is adirection coming close to the transmission, in top plan view; the singleexhaust pipe portion curves to allow an exhaust downstream region of thesingle exhaust pipe portion to be oriented toward a vehicle-front side,in top plan view; and the downstream exhaust pipe is connected to anexhaust downstream end of the exhaust gas-purifying unit, and disposedto extend from a connection portion thereof with the exhaustgas-purifying unit toward an tunnel opening formed in avehicle-widthwise central region of a lower end of a dash panel of thevehicle.
 2. The exhaust apparatus as defined in claim 1, wherein: theexhaust gas-purifying unit has a catalyst installation portion formed ina cross-sectionally generally circular shape and provided in the gaspassage; and a maximum vehicle-widthwise protruding amount of the singleexhaust pipe portion with respect to an exhaust upstream end surface ofthe catalyst installation portion is set to be greater than a maximumvehicle-widthwise protruding amount of the downstream exhaust pipe withrespect to an exhaust downstream end surface of the catalystinstallation portion, to allow a gas entry angle with respect to theexhaust upstream end surface of the catalyst installation portion tobecome greater than a gas discharge angle with respect to the exhaustdownstream end surface of the catalyst installation portion.
 3. Theexhaust apparatus as defined in claim 2, wherein the exhaustgas-purifying unit is disposed on the vehicle-front side of an exhaustupstream end of the single exhaust pipe portion and below the branchpipe portions.
 4. The exhaust apparatus as defined in claim 3, wherein:the exhaust gas-purifying unit is supported with respect to the engine;and the downstream exhaust pipe has a flexible joint interposed therein.5. The exhaust apparatus as defined in claim 4, wherein: the upstreamexhaust assembly has a plurality of intermediate collector pipe portionsbetween each of the plurality of branch pipe portions and the singleexhaust pipe portion; each of the intermediate collector pipe portionsis formed by dividing the plurality of cylinders into a plurality ofcylinder groups each consisting of two or more cylinders whose exhauststrokes are not successive with respect to each other, and merging thebranch pipe portions communicated with respective ones of the cylindersin each of the cylinder groups, on a cylinder group-by-cylinder groupbasis; the single exhaust pipe portion is formed by merging theplurality of intermediate collector pipe portions together; and each ofthe plurality of intermediate collector pipe portions curves to allow anexhaust downstream region of the intermediate collector pipe portion tobe oriented toward one side of the vehicle-widthwise direction which isa direction coming close to the transmission, in top plan view.
 6. Theexhaust apparatus as defined in claim 4, wherein: the section of theupstream exhaust assembly on the exhaust upstream side of the singleexhaust pipe portion is comprised of the branch pipe portions; thesingle exhaust pipe portion is formed by merging the plurality of branchpipe portions together; and each of the plurality of branch pipeportions curves to allow an exhaust downstream region of the branch pipeportion to be oriented toward one side of the vehicle-widthwisedirection which is a direction coming close to the transmission, in topplan view.
 7. The exhaust apparatus as defined in claim 1, wherein theexhaust gas-purifying unit is disposed on the vehicle-front side of anexhaust upstream end of the single exhaust pipe portion and below thebranch pipe portions.
 8. The exhaust apparatus as defined in claim 7,wherein: the exhaust gas-purifying unit is supported with respect to theengine; and the downstream exhaust pipe has a flexible joint interposedtherein.
 9. The exhaust apparatus as defined in claim 1, wherein: theupstream exhaust assembly has a plurality of intermediate collector pipeportions between each of the plurality of branch pipe portions and thesingle exhaust pipe portion; each of the intermediate collector pipeportions is formed by dividing the plurality of cylinders into aplurality of cylinder groups each consisting of two or more cylinderswhose exhaust strokes are not successive with respect to each other, andmerging the branch pipe portions communicated with respective ones ofthe cylinders in each of the cylinder groups, on a cylindergroup-by-cylinder group basis; the single exhaust pipe portion is formedby merging the plurality of intermediate collector pipe portionstogether; and each of the plurality of intermediate collector pipeportions curves to allow an exhaust downstream region of theintermediate collector pipe portion to be oriented toward one side ofthe vehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.
 10. The exhaust apparatus as defined inclaim 1, wherein: the section of the upstream exhaust assembly on theexhaust upstream side of the single exhaust pipe portion is comprised ofthe branch pipe portions; the single exhaust pipe portion is formed bymerging the plurality of branch pipe portions together; and each of theplurality of branch pipe portions curves to allow an exhaust downstreamregion of the branch pipe portion to be oriented toward one side of thevehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.
 11. The exhaust apparatus as defined inclaim 2, wherein: the upstream exhaust assembly has a plurality ofintermediate collector pipe portions between each of the plurality ofbranch pipe portions and the single exhaust pipe portion; each of theintermediate collector pipe portions is formed by dividing the pluralityof cylinders into a plurality of cylinder groups each consisting of twoor more cylinders whose exhaust strokes are not successive with respectto each other, and merging the branch pipe portions communicated withrespective ones of the cylinders in each of the cylinder groups, on acylinder group-by-cylinder group basis; the single exhaust pipe portionis formed by merging the plurality of intermediate collector pipeportions together; and each of the plurality of intermediate collectorpipe portions curves to allow an exhaust downstream region of theintermediate collector pipe portion to be oriented toward one side ofthe vehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.
 12. The exhaust apparatus as defined inclaim 2, wherein: the section of the upstream exhaust assembly on theexhaust upstream side of the single exhaust pipe portion is comprised ofthe branch pipe portions; the single exhaust pipe portion is formed bymerging the plurality of branch pipe portions together; and each of theplurality of branch pipe portions curves to allow an exhaust downstreamregion of the branch pipe portion to be oriented toward one side of thevehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.
 13. The exhaust apparatus as defined inclaim 3, wherein: the upstream exhaust assembly has a plurality ofintermediate collector pipe portions between each of the plurality ofbranch pipe portions and the single exhaust pipe portion; each of theintermediate collector pipe portions is formed by dividing the pluralityof cylinders into a plurality of cylinder groups each consisting of twoor more cylinders whose exhaust strokes are not successive with respectto each other, and merging the branch pipe portions communicated withrespective ones of the cylinders in each of the cylinder groups, on acylinder group-by-cylinder group basis; the single exhaust pipe portionis formed by merging the plurality of intermediate collector pipeportions together; and each of the plurality of intermediate collectorpipe portions curves to allow an exhaust downstream region of theintermediate collector pipe portion to be oriented toward one side ofthe vehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.
 14. The exhaust apparatus as defined inclaim 3, wherein: the section of the upstream exhaust assembly on theexhaust upstream side of the single exhaust pipe portion is comprised ofthe branch pipe portions; the single exhaust pipe portion is formed bymerging the plurality of branch pipe portions together; and each of theplurality of branch pipe portions curves to allow an exhaust downstreamregion of the branch pipe portion to be oriented toward one side of thevehicle-widthwise direction which is a direction coming close to thetransmission, in top plan view.